Certain medical conditions are known to exist that make individuals prone to pulmonary embolisms. These conditions include susceptibility to deep vein thrombosis resulting from prolonged immobility (potentially exacerbated by lack of fluids). The unexpected death in 2003 of journalist David Bloom (being in a relatively immobile and most likely in a somewhat dehydrated condition while in a military type vehicle during the 2003 war in IRAQ) and unexpected attacks in 1994 and 1998 (both non-fatal) reportedly experienced by Vice President Dan Quayle from a prolonged air flight (due to a condition sometimes referred to as “economy class syndrome” in reference to seating with limited leg room in economy class but equally applicable to any relatively immobile seating or position) demonstrate anyone's susceptibility to such conditions. While it has been recommended that passengers periodically move around the cabin during prolonged air flights to avoid such problems, the capability of an individual to move sufficiently to avoid such problems may be limited or impossible, e.g., in a war environment.